Synthesis and Catalytic Behavior in the Propylene Polymerization Reaction

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Synthesis and Catalytic Behavior in the Propylene Polymerization Reaction

Martin Schl¨ogl and Bernhard Rieger

University of Ulm, Department of Materials and Catalysis, Albert-Einstein-Allee 11, D-89069 Ulm, Germany

Reprint requests to Prof. Dr. B. Rieger. Fax: +49 (0)731 5023039.

E-mail: bernhard.rieger@chemie.uni-ulm.de

Z. Naturforsch. 59b, 233 – 240 (2004); received October 20, 2003

The synthesis of a series of C₁-symmetric metallocene complexes rac-[1-(5,6-dialkoxy-2-methyl- 1-η⁵-indenyl)-2-(9-η⁵-fluorenyl)ethane]zirconium dichlorides (alkyl: n-butyl, n-hexyl, n-octyl, n- decyl) is described. These complexes are versatile catalysts in the polymerization of propylene af- ter in situ activation with triisobutylaluminum (TIBA) and Ph₃C[B(C₆F₅)₄] in toluene and heptane solution. All catalysts show higher solubility and improved polymerization properties in industrially used hydrocarbon solvents (e.g. heptane). However, the molecular weights and isotacticity values of the resulting polypropylene materials are decreased compared to the ethoxy-bridged analogue rac- [1-(5,6-ethylenedioxy-2-methyl-η⁵-indenyl)-2-(9-η⁵-fluorenyl)ethane]zirconium dichloride. A possible explanation is based on enhanced interaction of the active catalyst centers with Al(III) scavenger molecules even at low Al : Zr ratios, leading to reversible chain transfer.

Key words: Metallocene Catalysis, Dialkoxy Substitution, Propylene Polymerization

Introduction

One significant advantage in metallocene polymerization catalysis [1] is the easy possibility to design polymer microstructures and the corresponding material properties by variation of the catalyst structure.

This can be performed by various methods. The nature of the cocatalyst [2] certainly plays a decisive role as well as the variation of the ligand framework [3].

Recently, we published a series of papers on asymmetric, ”dual-side“, catalysts that produce high perfor- mance polypropylene elastomers [4]. Here, a substitution in 5,6-position of the indenyl moiety has a ma- jor influence on the polymerization properties concerning a shift to higher molecular weight PP materials.

However, the partially reduced solubility of these compounds in hydrocarbon solvents, like hexane or heptane, hinders a broader application [5, 6]. In this con- text we synthesized a series of zirconocene derivatives containing 5,6-di(n-alkoxy)indenyl ligands [7, 8] and tested their catalytic behavior in the polymerization of propylene in toluene and heptane solution revealing significant changes compared to their non-alkoxy- substituted counterparts and to an ethoxy-bridged analogue.

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Results and Discussion Ligand synthesis

The 1,2-ethylidene-bridged, fluorenyl-indenyl lig- ands 7a – d are built up from the 5,6-dialkoxyindene anions and an equimolar amount of 9-(2-bromoethyl)- fluorene 6 via a convergent route (Scheme 1). The flu- orene derivative 6 is obtained by a modified litera- ture procedure from fluorene after deprotonation with n-BuLi and treatment with excess 1,2-dibromoethane.

The indene derivatives are formed within several steps: The etherification of 1 with the correspond- ing n-alkyl bromide (10 mol-% excess) using K₂CO₃ in DMF gives the dialkoxybenzenes. A subsequent Friedel-Crafts cycloacylation with methacroyl chloride at−78^◦C leads to the indanones 3a – d using AlCl₃as Lewis acid in 10 mol-% excess. Lower quantities result in non-cyclic side products, whereas higher amounts of aluminum chloride cause partially cleavage of the ether functionalities. The synthesis of the diastereomeric in- danoles 4a – d is performed quantitatively by reduction with NaBH₄. These are transformed directly to the de- sired indene precursors 5a – d by dehydration with p- toluenesulfonic acid at 70^◦C.

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Scheme 1. Ligand synthesis.

Synthesis of zirconium complexes

The synthesis of the rac-[1-(5,6-dialkoxy-2-methyl- 1-η⁵-indenyl)-2-(9-η⁵-fluorenyl)ethane] zirconocene dichlorides 8a – d is performed by deprotonation of compounds 7a – d and treatment with an equimolar amount of ZrCl₄(Scheme 2). Re-crystallization from toluene or toluene/hexane mixtures give the orange, solid products in good to moderate yield [9].

Scheme 2. Catalyst synthesis.

Polymerization reactions

The propylene polymerization behavior of com- plexes 8a – d is tested at various temperatures and monomer concentrations in toluene and heptane solution. The results are compared to an analogous set of experiments using a similar catalyst structure containing an ethylene dioxid group at the 5,6-position of the indenyl moiety 9 (Formula 3). Activation is performed by in situ treatment with triisobutylalu-

minum (TIBA; ratio 100:1) and subsequent addition of Ph₃C[B(C₆F₅)₄] (ratio 10:1). Complete alkylation with TIBA proceeds only after heating for one hour at 50^◦C, which nearly doubles polymerization activities, compared to experiments without preliminary heating.

The polymerizations were repeated several times with reproducible results [10].

Formula 3.

The polymerization behavior of catalysts 8a – d in toluene solution (Table 1: Run 1 – 18) comprises moderate catalyst activities at 30 ^◦C with no significant variation concerning the monomer pressure, but can be enhanced by a factor of 2 by raising the polymerization temperature to 50^◦C. The isotacticity values are at both temperatures in the range of 10 – 15% revealing atactic material. The obtained molecular weights are between 20000 and 70000 g/mol and show no significant dependency on the monomer pressure, temperature and variation of the alkoxy-chain length. The results are compared to an analogue set of polymeriza- tion reactions in toluene using structure 9 (Fig. 3). This catalyst is known to polymerizeα-olefins according to

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Table 1. Polymerization results with 8a – d and 9 / TIBA / Ph3C[B(C6F5)4] in toluene.

Run Cat. Amount Temp. Pressure [C3] Yield tp Mwa PD Activity^b [mmmm]^c

[µ^mol] ^[^◦^C] ^[bar] ^[g/mol] ^[g] ^[h]

1 8a 5 30 3.0 1.3 2.63 0.52 20000 1.7 800 11.3

2 8a 5 30 5.0 3.0 7.89 0.75 50000 4.7 700 10.0

3 8a 10 30 7.0 5.0 8.43 0.43 30000 3.6 800 11.6

4 8a 5 50 6.5 3.0 7.69 0.30 40000 3.5 1700 12.0

5 8b 10 30 3.0 1.3 10.13 0.91 30000 4.2 900 11.2

6 8b 10 30 5.0 3.0 7.50 0.50 30000 4.6 500 12.2

7 8b 10 30 7.0 5.0 7.50 0.51 30000 3.6 300 10.4

8 8b 5 50 6.5 3.0 7.50 0.30 40000 5.9 1700 12.6

9 8c 10 30 3.0 1.3 8.44 1.00 40000 2.9 700 10.3

10 8c 10 30 5.0 3.0 11.25 0.67 40000 2.8 600 10.6

11 8c 10 30 7.0 5.0 11.25 0.58 40000 2.7 900 10.9

12 8c 5 40 5.7 3.0 11.25 0.50 40000 3.1 1500 11.8

13 8c 5 50 6.5 3.0 11.25 0.30 50000 4.8 2500 14.9

14 8d 10 30 3.0 1.3 7.50 0.83 40000 2.7 600 10.8

15 8d 10 30 5.0 3.0 7.50 0.70 40000 3.5 400 11.2

16 8d 10 30 7.0 5.0 7.50 0.55 40000 3.3 300 13.4

17 8d 5 40 5.7 3.0 11.25 0.55 50000 3.7 1400 12.6

18 8d 5 50 6.5 3.0 11.25 0.28 70000 4.3 2700 15.3

19 9 2 30 3.0 1.3 2.70 0.50 120000 2.0 2100 50.7

20 9 2 30 5.0 3.0 4.50 0.50 130000 3.2 1500 43.9

21 9 2 30 7.0 5.0 9.00 1.00 160000 3.5 1000 43.3

22 9 2 50 6.5 3.0 8.70 0.50 100000 2.9 2900 63.3

aRelative against PP standards;^bkg PP/[molZr]*[C3]*h;^cisotacticity [%].

Table 2. Polymerization results with 8d / TIBA / Ph3C[B(C6F5)4] in heptane.

Run Cat. Amount Temp. Pressure [C3] Yield tp Mwa PD Activity^b [mmmm]^c

[µ^mol] ^[^◦^C] ^[bar] ^[g/mol] ^[g] ^[h]

23 8d 10 30 3.0 0.7 6.19 0.88 30000 4.0 1000 9.7

24 8d 10 30 5.0 1.7 9.38 0.35 50000 3.4 1600 9.6

25 8d 5 30 7.0 3.0 9.38 0.27 70000 2.4 2300 8.1

26 8d 10 50 4.0 0.7 9.38 0.33 30000 6.1 4100 12.7

aRelative against PP standards;^bkg PP/[molZr]*[C3]*h;^cisotacticity [%].

the earlier proposed “back-skip” mechanism. Here, the polymerizations expose results expected for this catalyst family (Table 1: Run 19 – 22). Molecular weights are enhanced by approximately a factor of 2 compared to 8a – d and higher M_W values are obtained at lower temperatures. The most explicit differences occur at the PP isotacticities: Complex 9 produces PP compris- ing [mmmm] sequences from 50% to 65% and the isotacticities increase at the higher temperatures, as expected [4]. Also the declining [mmmm] values with higher monomer concentration at polymerization temperatures of 30^◦C are typical for the “back-skip” polymerization mechanism.

The n-alkoxy substituted metallocenes 8a – d reveal a significantly increased solubility in hydrocarbon sol- vents (hexane, heptane) compared to 9. Solubility tests of 8a – d in heptan gave clear solutions within concen-

trations of 1 – 10µm/ml. Experiments with 9 showed only insufficient catalyst solubility under these conditions and therefore, no catalyst activity in propylene polymerizations occurred. Exemplary polymerization experiments of 8d in heptane solution (Table 2) were performed under conditions similar to run 1 – 22 (Ta- ble 1). The resulting molecular weights (M_W: 30000 – 70000 g/mol) and isotacticity values ([mmmm]: ap- prox. 10%) are completely in the same range compared to polymerization experiments in toluene. How- ever, there are significantly increased polymer yields (up to factor 8) relative to experiments in toluene.

A probable explanation for these unexpected experimental results might be seen in an enhanced interaction of active sites with aluminum scavenger molecules [11]. In MAO activated polymerization reactions with 9 [4b] in toluene a reversible chain transfer to Al cen-

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ters is supported by deuterium labeling experiments.

Such a reversible transport process results in lower M_W and [mmmm] values, due to the existence of the two enantiomeric zirconocene species with opposite enan- tiofacial discrimination of prochiral propene monomer molecules [12]. Reduced Al : catalyst ratios within in situ TIBA/borate activation method of 9 suppress this transfer effect and lead again to higher tacticities and molecular weights. Apparently, different cir- cumstances exist in polymerizations using 8a – d and TIBA/Ph₃C[B(C₆F₅)₄]: Here, molecular weights and isotacticities of the obtained polymer materials are low, even after MAO-free activation processes. A possible explanation for this effect might be found in the am- phiphilic nature of the catalyst sites, bearing polar “Zr- head functions” and apolar n-alkoxy substituents. In apolar media, in our case especially in heptane, this might lead to a close contact of oxygen-substituted zirconocenium centers and Al(III)-activator molecules via formation of (e.g. inverse micellar) aggregates.

This assumption proposal cannot be supported experi- mentally (light scattering, etc.) yet, due to the high sen- sitivity of the cationic catalyst sites.

Conclusion

Here we present a series of new, C₁-symmetric metallocene complexes containing diverse 5,6-di(n- alkoxy)indenyl ligands. These structures are versatile catalysts for the polymerization of propy- lene in toluene and heptane solution using in situ TIBA/Ph₃C[B(C₆F₅)₄] activation. The introduction of apolar alkyl segments into the ligand structure leads to a good solubility in hydrocarbon solvents compared to non-alkyl substituted counterparts. Additionally, the resulting polymerization activities of 8a – d in heptane can be enhanced compared to experiments in toluene.

This is an advantageous fact as hydrocarbons like heptane can be used as solvents in industrial polymerization processes. However, the obtained polypropy- lenes reveal significant changes in the catalyst properties compared to similar non-substituted structures resulting in reduced polymer molecular weights and isotacticities. A hypothetical explanation is based on an extended interaction between Lewis acidic Al centers of the TIBA co-activator and the active catalyst.

This would lead to a reversible chain transfer, which is accepted for analogue systems and results in reduced M_W- and [mmmm] values. The synthesis of analogous catalyst structures bearing n-alkyl-substituted indenyl

moieties is underway to suppress the influences of Al- coordination at oxygen containing ligand fragments.

Experimental Section General remarks

The rac-[1-(5,6-ethylenedioxy-2-methyl-η⁵-indenyl)-2- (9-η⁵- fluorenyl)ethane]zirconium dichloride 9 [4b] and Ph3C[B(C6F5)4] [13] were synthesized according to lit- erature procedures, 9-(2-bromoethyl)-fluorene 6 [14] and the 1,2-dialkoxybenzenes 2a – d [15] according to modified literature methods. All synthetical work (except the syn- thesis of 2a – d) was done using standard Schlenk tech- niques under argon atmosphere. The 1-bromoalkanes, 1,2- dihydroxybenzene, methacroyl chloride, p-toluenesulfonic acid, fluorene, 1,2-dibromoethane, n-BuLi (1.6 molar in hex- ane), K₂CO₃, Na₂SO₄, NaBH₄, AlCl₃and ZrCl₄were purchased from Aldrich. Triisobutylaluminum (1 molar in hexane) was purchased from Crompton, solvents for synthesis and polymerizations were purchased from Merck and dried via distillation over LiAlH4.

NMR analysis of the prepared compounds was performed on a Bruker DRX 400 spectrometer at ambient temperatures and referenced to the CDCl3solvent signal. Elemental analysis (Vario EL Elementar) and mass spectra (Finnigan MAT SSQ 7000) were determined by the Microanalytical Lab- oratory of the University of Ulm. PP analysis: ¹³C NMR spectra were recorded on a Bruker AMX 500 spectrometer (C2D2Cl4, 90^◦C, 125 MHz, 5 mm probe) in the invers gated decoupling mode with a 3 s pulse delay and a 45^◦C pulse to attain conditions close to the maximum signal-to-noise ratio. Molecular weights and molecular weight distributions were determined by gel permeation chromatography (GPC, Waters 2000, 140^◦C in 1,2,4-trichlorobenzene) relative to polypropylene standards.

Synthesis

1 , 2 - D i a l k o x y b e n z e n e s 2a – d

A suspension of 750.0 mmol (M: 138.21 g/mol; 103.66 g) of K2CO3, 250.0 mmol (M:110.11 g/mol; 27.53 g) of 1,2- dihydroxybenzene 1 and 600.0 mmol of 1-bromoalkane in 500 ml of DMF was stirred for 12 h at 80^◦C in a 2 l round- bottom flask with reflux condenser. After cooling to room temperature 500 ml of H2O und 800 ml of Et2O was added.

After separation of remaining inorganic salts the H₂O / DMF phase was washed with 200 ml of water. The combined ether phases were extracted with 2×200 ml of H2O and distilled to dryness.

2a: Yield: 48.20 g (M: 222.33 g/mol; 217.1 mmol; 86.9%) red oil. –¹H NMR (400 MHz, CDCl3):δ=1.02 (t, 6H, CH₃), 1.54 (m, 4H, -CH₂CH₃), 1.83 (m, 4H, -OCH₂CH₂-), 4.03 (q, 4H, -OCH2), 6.91 (s, 4H, Har). – ¹³C NMR

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(400 MHz, CDCl3): δ = 14.4, 19.8; 32.0, 69.5, 114.8, 114.8, 121.6, 149.9. – MS (GC-MS): m/z=222 [M⁺]. – C14H22O2: calcd. C 75.63, H 9.97; found C 75.49, H 9.81.

2b: Yield: 62.91 g (M: 278.44 g/mol; 226.3 mmol;

90.5%) red liquid. –¹H NMR (400 MHz, CDCl₃): δ = 0.93 (t, 6H, CH3), 1.36 (m, 8H, -CH2CH2CH3), 1.51 (m, 4H, -OCH₂CH₂CH₂-), 1.83 (m, 4H, -OCH₂CH₂-), 4.00 (t, 4H, -OCH2), 6.89 (s, 4H, Har). – MS (GC-MS): m/z= 278 [M⁺]. – C18H30O2: calcd. C 77.65, H 10.86; found C 77.62, H 10.79.

2c: Yield: 52.28 g (M: 334.55 g/mol; 157.4 mmol; 62.9%) red oil. – ¹H NMR (400 MHz, CDCl₃): δ = 0.89 (t, 6H, CH3), 1.30 (m, 16H, -(CH2)4CH3), 1.48 (m, 4H, - OCH2CH2CH2-), 1.81 (m, 4H, -OCH2CH2-), 3.99 (t, 4H, - OCH2), 6.88 (s, 4H Har). –¹³C NMR (400 MHz, CDCl3):

δ=13.9, 22.4, 22.5, 22.6, 26.0, 28.1, 28.7, 69.2, 114.1, 114.4, 120.9, 149.2. – MS (GC-MS): m/z=334 [M⁺]. – C22H38O2: calcd. C 78.99, H 11.45; found C 78.91 H, 11.30.

2d: Yield: 12.18 g (M: 390.66 g/mol; 187.3 mmol; 74.9%) white needles after re-crystallization in 100 ml of EtOH.¹H NMR (400 MHz, CDCl3):δ=0.91 (t, 6H, CH3), 1.20 – 1.55 (m, 28H, CH₂), 1.71 – 1.90 (m, 4H, -O-CH₂CH₂-), 3.98 (t, 4H, -OCH2-), 6.89 (s, 4H, Har). –¹³C NMR (400 MHz, CDCl₃):δ=14.2, 22.8, 26.2, 29.4, 29.5, 29.6, 29.7, 29.7, 32.0, 69.4, 114.3, 114.3, 121.1, 149.4. – C26H46O2: calcd. C 79.94 H 11.87; found C 80.02 H 11.41.

5 , 6 - D i a l k o x y - 2 - m e t h y l i n d a n - 1 - o n e s 3a – d 14.67 g of AlCl3(M: 133.34 g/mol; 110 mmol) were sus- pended in 100 ml of dichloromethane in a 500 ml Schlenk flask, the mixture was cooled to−78^◦C and 100 mmol of methacroyl chloride was added. A solution of 100 mmol of 1,2-dialkoxybenzene in 100 ml of CH2Cl2 was added over 1 h. After stirring 12 h at room temperature the suspension was cooled to−78^◦C and hydrolyzed with 100 ml of H2O.

The organic phase was washed with 2×100 ml of water, dried with Na₂SO₄and evaporated to dryness.

3a: Yield: 13.13 g (M: 290.41 g/mol; 45.2 mmol; 45,2%) white solid after re-crystallization from 50 ml of EtOH and washing with 20 ml of MeOH.¹H NMR (400 MHz, CDCl₃):

δ=0.94 (t, 6H, CH3 “chain”), 1.26 (s, 3H, CH3-indenyl), 1.48 (m, 4H, -OCH₂CH₂CH₂-), 1.80 (m, 4H, -OCH₂-CH₂), 2.60 (m, 2H, CH2-indenyl), 3.21 (m, 1H, CH-indenyl), 4.00 (t, 4H,−OCH₂-), 6.80 (s, 1H, Har), 7.13 (s, 1H, Har). –

13C NMR (400 MHz, CDCl3): δ=14.5, 17.3 19.9, 31.6, 35.4, 42.9, 69.5, 106.8, 109.2, 129.4, 149.1, 149.9, 156.3, 208.9. – MS (GC-MS): m/z=291 [M⁺]. – C18H26O3: calcd.

C 74.45, H 9.02; found C 74.41, H 8.99.

3b: Yield: 11.89 g (M: 346.51 g/mol; 34.36 mmol; 34.4%) white solid after re-crystallization in 50 ml of EtOH and washing with 20 ml of MeOH.¹H NMR (400 MHz, CDCl3):

δ=0.90 (t, 6H, CH₃ “chain”), 1.23 (s, 3H, CH₃-indenyl), 1.35 – 1.55 (m, 12H, -OCH2CH2(CH2)3-), 1.90 (m, 4H,

−OCH2CH2-), 2.66 (m, 2H, CH2-indenyl), 3.29 (m, 1H, CH- indenyl), 4.01 (dt, 4H, -OCH₂-), 6.75 (s, 1H, Har), 7.10 (s, 1H, Har). –¹³C NMR (400 MHz, CDCl3):δ=14.3, 17.0, 22.9, 22.9, 25.9, 26.0, 29.2, 29.3, 31.8, 31.8, 35.1, 42.6, 69.4, 69.5 106.5, 108.9, 129.1, 148.8, 149.1, 149.9, 156.0, 208.6. – MS (GC-MS): m/z=347 [M⁺]. – C22H34O3: calcd.

C 76.26, H 9.89; found C 76.13, H 9.80.

3c: Yield: 15.17 g (M: 402.62 g/mol; 37.67 mmol;

37.7%) white solid after re-crystallization in 50 ml of MeOH.¹H NMR (400 MHz, CDCl₃):δ=0.83 (t, 6H, CH₃

“chain”), 1.23 (s, 3H, CH3-indenyl), 1.25 – 1.35 (m, 20H, -OCH₂CH₂(CH₂)5-), 1.46 (m, 4H, -OCH₂CH₂-), 2.52 (m, 2H, CH2-indenyl), 3.20 (m, 1H, CH-indenyl), 4.01 (dt, 4H, - OCH₂-), 6.83 (s, 1H, Har), 7.13 (s, 1H, Har). –¹³C NMR (400 MHz, CDCl3): δ =12.3, 14.9, 20.8, 24.2, 24.2, 10 signals at 27.2 – 30.0, 40.4, 67.3, 67.5, 104.4, 106.7, 112.7, 127.0, 146.7, 147.4, 153.9, 206.4. – MS (GC-MS): m/z= 403 [MH⁺]. – C26H42O3: calcd. C 77.56, H 10.51; found C 77.85, H 10.30.

3d: Yield: 19.28 g (M: 458.73 g/mol; 42.02 mmol;

42.0%) white solid after re-crystallization in 50 ml of MeOH.¹H NMR (400 MHz, CDCl₃):δ=0.81 (t, 6H, CH₃

“chain”), 1.23 (s, 3H, CH3-indenyl), 1.15 – 1.51 (m, 28H, -OCH2CH2(CH2)7-), 1.78 (m, 4H, -OCH2CH2-), 2.56 (m, 2H, CH2-indenyl), 3.20 (m, 1H, CH-indenyl), 3.98 (dt, 4H,

−OCH2-), 6.76 (s, 1H, Har), 7.10 (s, 1H, Har). – MS (GC- MS): m/z=460 [MH⁺]. – C₃₀H₅₀O₃: calcd. C 78.55, H 10.99; found C 78.40, H 10.91.

5 , 6 - D i a l k o x y - 2 - m e t h y l i n d a n - 1 - o l e s 4a-d 30.0 mmol of 3a – d and 30 mmol of NaBH₄ (M:

37.80 g/mol; 1.13 g) in 100 ml of EtOH were stirred for 24 h at room temperature in a 500 ml Schlenk flask. After neutral- ization with HCl, 100 ml of H2O and 100 ml of Et2O were added. The organic phase was separated and washed with 2×100 ml of water. Drying with Na2SO4and evaporating to dryness lead to white solids which were converted directly to the corresponding indenes 5a – d without purification.

5 , 6 - D i a l k o x y - 2 - m e t h y l i n d - 1 - e n e s 5a – d

The indanoles 4a – d were dissolved in 100 ml of toluene, 0.57 g of p-toluenesulfonic acid (M: 190.22; 3.0 mmol) was added and the mixture was stirred for 1 h at 70^◦C. After washing with 2×100 ml of H₂O and drying with Na₂SO₄ the solvent was removed via distillation.

5a: Yield: 3.98 g (M: 274.41 g/mol; 14.5 mmol; 48.3% re- garding to 3a) white crystals after re-crystallization in 30 ml of EtOH.¹H NMR (400 MHz, CDCl3): δ=0.96 (t, 6H, CH3“chain”), 1.49 (m, 4H, -OCH2CH2CH2-) 1.78 (m, 4H, -OCH2CH2-), 2.09 (s, 3H, CH3-indenyl), 3.19 (s, 2H, CH2- indenyl), 3.97 (t, 4H, -OCH2-), 6.36 (s, 1H, CH-indenyl), 6.81 (s, 1H, Har), 6.97 (s, 1H, Har). –¹³C NMR (400 MHz, CDCl3):δ=14.6, 17.3, 19.9, 32.2, 43.3, 70.2, 70.7, 107.5,

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112.3, 127.3, 136.6, 140.0, 145.4, 147.1, 149.3. – MS (GC- MS): m/z=274 [M⁺]. – C₁₈H₂₆O₂: calcd. C 78.79, H 9.55;

found C 78.74, H 9.56.

5b: Yield: 6.75 g (M: 330.52 g/mol; 20.4 mmol; 68.1%

regarding to 3b) white solid after re-crystallization in 20 ml of EtOH.¹H NMR (400 MHz, CDCl3):δ=0.89 (t, 6H, CH3

“chain”), 1.33 (m, 8H, -OCH2CH2CH2(CH2)3-), 1.47 (m, 4H, -OCH2CH2CH2-), 1.79 (m, 4H, -OCH2CH2-), 2.10 (s, 3H, CH₃-indenyl), 3.19 (s, 2H, CH₂-indenyl), 3.97 (t, 4H, - OCH2-), 6.35 (s, 1H, CH-indenyl), 6.81 (s, 1H, Har), 6.97 (s, 1H, Har). –¹³C NMR (400 MHz, CDCl₃):δ=14.7, 17.3, 23.3, 26.4, 30.2, 32.2, 42.3, 70.5, 71.0, 107.4, 112.3, 127.4, 136.6, 140.0, 145.4, 147.1, 149.2. – MS (GC-MS): m/z= 331 [M⁺]. – C22H34O2: calcd. C 79.95, H 10.37; found C 79.88, H 10.32.

5c: Yield: 7.61 g (M: 386.62 g/mol; 19.7 mmol; 65.6% re- garding to 3c) white needles after re-crystallization in 30 ml of MeOH.¹H NMR (400 MHz, CDCl₃):δ=0.83 (t, 6H, CH3“chain”), 1.29 (m, 16H, -OCH2CH2CH2(CH2)4-), 1.41 (m, 4H, -OCH2CH2CH2-), 1.75 (m, 4H, -OCH2CH2-), 2.01 (s, 3H, CH₃-indenyl), 3.10 (s, 2H, CH₂-indenyl), 3.95 (t, 4H, -OCH2-), 6.30 (s, 1H, CH-indenyl), 6.78 (s, 1H, Har), 6.90 (s, 1H, Har). –¹³C NMR (400 MHz, CDCl₃):δ=14.0, 16.6, 22.6, 29.2, 29.3, 29.4, 29.5, 31.7, 42.5, 69.7, 70.2, 104.4, 106.7, 111.5, 126.6, 125.8, 139.2, 144.6, 146.4, 148.5. – MS (GC-MS): m/z=386 [MH⁺]. – C26H42O2: calcd. C 80.77, H 10.95; found C 80.61, H 10.84.

5d: Yield: 7.78 g (M: 442.73 g/mol; 17.6 mmol; 58.6%

regarding to 3d) white solid after re-crystallization in 50 ml EtOH.¹H NMR (400 MHz, CDCl₃):δ=0.91 (t, 6H, CH₃

“chain”), 1.20 – 1.54 (m, 28H, -OCH2CH2(CH2)7-), 1.80 (m, 4H, -OCH₂CH₂-), 2.11 (s, 3H, CH₃-indenyl), 3.22 (s, 2H, CH2-Indenyl), 4.00 (m, 4H, -OCH2-), 6.36 (s, 1H, CH- indenyl), 6.82 (s, 1H, Har), 6.99 (s, 1H, Har). – MS (GC- MS): m/z=443 [MH⁺]. – C30H50O2: calcd. C 81.39, H 11.38; found C 81.21, H 11.29.

9 - ( 2 - B r o m o e t h y l ) - f l u o r e n e 6

10.00 g of fluorene (M: 166.22 g/mol; 60.2 mmol) were degassed in a 500 ml Schlenk flask with a dropping funnel and dissolved in 300 ml of Et2O. After cooling to−78^◦C 37.6 ml of n-BuLi (1.6 molar in hexane; 60.2 mmol) were added over 0.5 h. After stirring for 2 h at room temperature the mixture was cooled again to−78^◦C and 20.7 ml of 1,2- dibromoethane (M: 187.9 g/mol; 240.8 mmol;δ: 2.18) were added rapidly. Stirring for 12 h at room temperature lead to a yellow suspension, which was washed twice with 100 ml of H2O. Evaporation to dryness gave a brown solid, which was re-crystallized from 50 ml of pentane.

Yield: 13.14 g (M: 273.17; 48.1 mmol; 74.9%) yel- low solid. ¹H NMR (400 MHz, CDCl3): δ =2.53 (m, 2H, FluHCH₂CH₂-), 3.31 (t, 2H, -CH₂Br), 4.17 (t, 1H, FluH); 7.37, 7.42 and 7.78 (m, 8H, Har). – ¹³C NMR

(400 MHz, CDCl3):δ= 30.5, 36.6, 46.4, 120.1, 124.4, 127.2, 127.5, 141.1, 145.8. – MS (GC-MS): m/z=273 [MH⁺]. – C15H13Br: calcd. C 65.95, H 4.80; found C 65.89, H 4.77.

[ 1 - ( 5 , 6 - D i a l k o x y - 2 - m e t h y l i n d e n - 1 - y l ) - 2 - ( 9 - f l u o r e n y l ) ] e t h a n e s 7a – d

20,0 mmol of 5a – d were degassed and dissolved in 70 ml of a mixture of toluene/dioxane (10:1) in a 250 ml Schlenk flask. After cooling to−78^◦C 12.5 ml of n-BuLi (1.6 molar in hexane; 20.0 mmol) were added. The obtained suspension was stirred for 2 h at room temperature, trans- ferred to a dropping funnel and added to a solution of 9-(2- bromoethyl)fluorene 6 in 50 ml of toluene (250 ml Schlenk flask) via 2 h. The mixture was stirred at room temperature for 12 h and washed with 2×100 ml of water. The organic phase was dried with Na2SO4 and a yellow solid was obtained after removing the solvent.

7a: Yield: 5.74 g (M: 466.67 g/mol; 12.3 mmol; 61.55%) white powder after washing with 300 ml of isopropanol.¹H NMR (400 MHz, CDCl3):δ=0.99 (m, 6H, CH3-“chain”), 1.42 (m, 2H, CH2-bridge), 1.52 (m, 4H,−O(CH2)2CH2-), 1.69 (m, 2H, CH2-bridge), 1.80 (m, 4H,−OCH2CH2-), 1.87 (s, 3H, CH3-indenyl), 3.03 (t, 1H, CH-indenyl), 3.86 (t, 1H, FluH), 4.00 (m 4H −OCH₂-), 6.32 (s, 1H, olefinic CH- indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s, 1H, Har in- denyl), 7.25 – 7.75 (m, 8H, Har fluorenyl). – MS (GC-MS):

m/z=466 [M⁺]. – C33H38O2: calcd. C 84.94, H 8.21; found C 84.81, H 8.20.

7b: Yield: 7.97 g (M: 522.78 g/mol; 15.2 mmol; 76.4%) white solid after re-crystallization in 50 ml of isopra- panol. ¹H NMR (400 MHz, CDCl₃): δ = 0.92 (m, 6H, CH3-“chain”), 1.35 (m, 2H, CH2-bridge), 1.41 (m, 12H, -O(CH₂)2(CH₂)3-), 1.70 (m, 2H, CH₂-bridge), 1.80 (m, 4H, -OCH2CH2-), 1.88 (s, 3H, CH3-indenyl), 3.03 (t, 1H, CH- indenyl), 3.86 (t, 1H, FluH), 4.00 (m, 4H, -OCH₂-), 6.33 (s, 1H, olefinic CH-indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s, 1H, Har indenyl), 7.25 – 7.73 (m, 8H, Har fluorenyl). – MS (GC-MS): m/z=523 [M⁺]. – C37H46O2: calcd. C 85.01, H 8.87; found C 84.85, H 8.92.

7c: Yield: 7.92 g (M: 578.89 g/mol; 13.7 mmol; 68.4%) white solid after re-crystallization in 50 ml of ethanol.¹H NMR (400 MHz, CDCl3):δ=0.82 (m, 6H, CH3-“chain”), 1.22 (m, 20H, −O(CH2)2(CH2)5-), 1,25 (m, 2H, CH2- bridge), 1.40 (m, 4H, −OCH2CH2-), 1.60 (m, 2H, CH2- bridge), 1.81 (s, 3H, CH₃-indenyl), 2.96 (t, 1H, CH-indenyl), 3.79 (t, 1H, FluH), 3.92 (m, 4H, −OCH2-), 6.26 (s, 1H, olefinic CH-indenyl), 6.63 (s, 1H, Har Indenyl), 6.73 (s, 1H, Har indenyl), 7.20 – 7.69 (m, 8H, Har fluorenyl). – MS (GC- MS): m/z=579 [M⁺]. – C₄₁H₅₄O₂: calcd. C 85.07, H 9.40;

found C 84.80, H 9.08.

7d: Yield: 6.53 g (M: 634.99 g/mol; 10.3 mmol; 51.4%) white solid after re-crystallization in 80 ml of ethanol.

1H NMR (400 MHz, CDCl3): δ =0.89 (m, 6H, CH3

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“chain”), 1.28 (m, 28H,−O(CH2)2(CH2)7-), 1.48 (m, 2H, CH₂-bridge), 1.60 (m, 2H, CH₂-bridge), 1.75 (m, 4H,

−OCH2CH2-), 1.88 (s, 3H, CH3-indenyl), 3.03 (t, 1H, CH- indenyl), 3.86 (t, 1H, FluH), 4.00 (m, 4H,−OCH₂-), 6.34 (s, 1H, olefinic CH-indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s, 1H, Har indenyl), 7.21 – 7.78 (m, 8H, Har fluorenyl). – MS (GC-MS): m/z=634 [M⁺]. – C45H62O2: calcd. C 85.12, H 9.84; found C 85.02, H 9.87.

r a c - [ 1 - ( 5 , 6 - D i a l k o x y - 2 - m e t h y l - 1 -η⁵-i n d e n y l ) - 2 - ( 9 -η⁵- f l u o r e n y l ) e t h a n e ] z i r c o n i u m d i c h l o r - i d e s 8a – d

5.0 mmol of 7 a – d were degassed and dissolved in 80 ml of toluene/dioxane (10:1) in a 250 ml Schlenk flask. After cooling to−78^◦C 10.0 mmol of n-BuLi (1.6 molar in hex- ane; 6.3 ml) was added. The mixture was stirred for 2 h at room temperature and re-cooled to−78^◦C. Adding of 5.0 mmol solid ZrCl4, stirring at room temperature for 12 h and subsequent evaporation of the solvent lead to the rough product. The purification was performed according to follow- ing procedures:

8a: Washing with 2×50 ml of hot toluene resulted in a clear solution which was concentrated to a volume of 20 ml.

Cooling at−20 ^◦C over night gave an orange precipitate.

Yield: 0.93 g (M: 626.89 g/mol; 1.5 mmol; 29.56%).¹H NMR (400 MHz, CDCl₃):δ=0.91 and 1,06 (t, each 3H, CH3-“chain”), 1.43 and 1.59 (m, each 2H, -O(CH2)2CH2-), 1.75 and 1.90 (m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3- indenyl), 3.76 and 4.44 (m, each 1H, CH₂-bridge to indenyl;

diastereotope), 3.87 (t, 2H, CH2-bridge to fluorenyl), 4.07 (m, 4H, -OCH₂-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.88 (m, 8H, Har fluorenyl). – C₃₃H₃₆Cl₂O₂Zr: calcd. C 63.26, H 5.75; found C 63.87, H 5.86.

8b: After washing with 50 ml of toluene the clear solu- tion was evaporated to dryness. Re-crystallization from 20 ml of toluene/hexane (1:1) gave an orange solid. Yield: 0.82 g (M: 682.90 g/mol; 1.2 mmol; 23.33%).¹H NMR (400 MHz, CDCl3):δ=0.87 and 0.95 (t, each 3H, CH3-“chain”), 1.28, 1.41 and 1.56 (m, together 12H, -O(CH₂)₂(CH₂)3-), 1.75 and 1.91 (m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3- indenyl), 3.76 and 4.54 (m, each 1H, CH2-bridge to indenyl;

diastereotope), 3.86 (t, 2H, CH₂-bridge to fluorenyl), 4.06 (m, 4H, -OCH2-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.89 (m, 8H, Har fluorenyl). – C37H44Cl2O2Zr: calcd. C 67.07, H 6.65; found: C 67.24, H 6.56.

8c: After washing with 50 ml of toluene the clear so- lution was evaporated to dryness. Re-crystallization from 20 ml of toluene gave an orange solid. Yield: 2.22 g (M:

739.01 g/mol; 3.0 mmol; 60.12%).¹H NMR (400 MHz,

CDCl3): δ =0.86 (m, 6H, CH3-“chain”), 1.15 – 1.50 and 1.56 (m, together 20H, -O(CH₂)2(CH₂)5-), 1.76 and 1.89 (m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3-indenyl), 3.76 and 4.54 (m, each 1H, CH2-bridge to indenyl; diastereotope), 3.86 (t, 2H, CH₂-bridge to fluorenyl), 4.06 (m, 4H, -OCH₂-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.89 (m, 8H, Har fluo- renyl). – C41H52Cl2O2Zr: calcd. C 66.58, H 7.04; found C 66.18, H 7.07.

8d: After washing with 50 ml of toluene the clear so- lution was evaporated to dryness. Re-crystallization from 20 ml of toluene gave an orange solid. Yield: 1.70 g (M:

795.11 g/mol; 2.1 mmol; 42.86%). ¹H NMR (400 MHz, CDCl₃): δ =0.86 (m, 6H, CH₃-“chain”), 1.15 – 1.50 and 1.55 (m, together 28H, -O(CH2)2(CH2)7-), 1.76 und 1.89 (m, each 2H, -OCH₂CH₂-), 2.14 (s, 3H, CH₃-indenyl), 3.76 and 4.52 (m, each 1H, CH2-bridge to indenyl; diastereotope), 3.85 (t, 2H, CH₂-bridge to fluorenyl), 4.05 (m, 4H, -OCH₂-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.89 (m, 8H, Har fluo- renyl). – C45H60Cl2O2Zr: calcd. C 67.92, H 7.55; found C 68.02, H 7.66.

Propylene polymerizations

All reactions were performed in a 0.5 l B¨uchi steel reactor at constant pressure (±0.1 bar) and temperature (±1^◦C).

First the desired amount of dichloro-zirconocene precursor was dissolved in 10 ml of dry solvent under argon atmosphere in a Schlenk flask and 100 equivalents of TIBA were added. This solution was injected into the autoclave, which had been charged with 200 ml of the corresponding solvent. After stirring at 50^◦C for one hour, the polymerization temperature was adjusted and the reactor was floated with propene up to the desired partial pressure. The polymerizations were started by injecting the appropriate amount of PhC₃⁺[B(C₆F₅)₄]⁻(10 mmol/ml in toluene) via a pres- sure burette. The monomer consumption was measured by a calibrated gas flow meter (Bronkhorst F-111C-HA-33P), and the pressure was kept constant during the entire polymerization period (Bronkhorst pressure controller P-602C- EA-33P). Pressure, temperature and consumption of propene were monitored and recorded online. The polymerization reactions were quenched by injecting 1 ml methanol. Reac- tion mixtures were poured into acidified methanol (500 ml) and the polymer precipitated. The product was filtered, washed with excess methanol and dried in vacuum at 50^◦C overnight.

Acknowledgement

The authors thank DFG “Deutsche Forschungsgemein- schaft”, SFB 569, for financial support of this research.

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[1] For recent reviews see: a) H. H. Brintzinger, D. Fischer, R. M¨ulhaupt, B. Rieger, R. M. Waymouth, Angew.

Chem. Int. Ed. 34, 1143 (1995); b) L. Resconi, L. Cav- allo, A. Fait, F. Piemontesi, Chem. Rev. 100, 1253 (2000).

[2] a) Y.-X. E. Chen, T. J. Marks, Chem. Rev. 100, 1391 (2000); b) J .N. Pedeutour, K. Radhakrishan, H. Cra- mail, A. Deffieux, Macromol. Rapid Commun. 22, 1095 (2001); c) Y.-X. E. Chen, M. V. Metz, L. Li, C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 120, 6287 (1998).

[3] E. g.: H. G. Alt, A. K¨oppl, Chem. Rev. 100, 1205 (2000) and references therein.

[4] a) U. Dietrich, M. Hackmann, B. Rieger, M. Klinga, M. Leskel¨a, J. Am. Chem. Soc. 121, 4348 (1999);

b) K. Kukral, P. Lehmus, M. Klinga, M. Leskel¨a, B. Rieger, Eur. J. Inorg. Chem. 1349 (2002);

c) B. Rieger, C. Troll, J. Preuschen, Macromolecules 35(15), 5742 (2002).

[5] Aromatic solvents are difficult to separate from the polymer product due to their relatively high boiling points. Therefore, lower boiling (and less toxic) aliphatic hydrocarbons are predominantly used in industrial processes. Here, the insufficient solubility of metallocene catalyst compounds is considered to be a problem, which hinders a broader application. See:

M. K. Gosh, S. J. Maiti, Polym. Mater. 16, 113 (1999).

[6] Examples for heptane as a polymerization solvent:

a) Y. X. Chen, M. D. Rausch, J. C. W. Chien, J. Polym.

Sci. A 33, 2093 (1995); b) A. R. Siedle, W. M.

Lamanna, R. A. Newmark, J. Stevens, D. E. Richard- son, M. Ryan, Makromol. Chem. Macromol. Symp. 66, 215 (1993).

[7] For other oxygen substituted metallocene catalysts see: a) N. Piccolrovazzi, P. Pino, G. Consiglio, A. Sironi, M. Moret, Organometallics 9, 3098 (1990);

b) I. K. Lee, W. J. Gauthier, J. A. M. Ball, B. Iyen- gar, S. Collins, Organometallics 11, 2115 (1992);

c) P. Lehmus, E. Kokko, O. Härkki, R. Leino, H. J. G. Luttikhedde, J. H. Näsman, J. Seppälä, Macro- molecules 32, 3547 (1999); d) E. Kokko, P. Lehmus, R. Leino, H. J. G. Luttikhedde, P. Ekholm, J. H.

N¨asman, J. Seppal¨a, Macromolecules 33, 9200 (2000).

[8] Asymmetric complexes are easily accessible, also in larger quantities, relative to their C2-symmetric ana- logues: There is no material- and time-consuming sep- aration of rac- and meso-species, which might be espe- cially difficult or even impossible for alkyl-substituted rac-derivatives.

[9] Purification of corresponding complexes with shorter alkoxy substituents at 5,6-position (e.g.: ALK = ethyl) failed due to insufficient solubility in apolar solvents.

[10] Activity values and molecular weight averages:±15%;

isotacticities:±5%.

[11] A second hypothesis might be seen in a change of the polymerization mechanism by this 5,6-dialkoxy sub- stitution. The long, flexible n-alkyl substituents might cause an increased interaction with the growing polymer chain. However, this assumption cannot explain the reduced isotacticity values with 8a – d as well as the lack of influence of the polymerization temperature and the length of the n-alkyl substituents on the poly- mer properties.

[12] For analogue examples of reversible chain transfer reactions, see: a) S. Lieber, H. H. Brintzinger, Macromolecules 33, 9192 (2000); b) J. C. W. Chien, Y. Iwamoto, M. D. Rausch, W. Wedler, H. H. Winter, Macromolecules 30, 3447 (1997); c) J. C. W. Chien, Y. Iwamoto, M. D. Rausch, J. Polym. Sci. A. 37, 2436 (1999); d) C. Przybyla, G. Fink, Acta Polym. 50, 77 (1999).

[13] J. C. W. Chien, W. M. Tsai, M. D. Rausch, J. Am.

Chem. Soc. 113, 8570 (1991).

[14] B. Peifer, W. Milius, H. G. Alt, J. Organomet. Chem.

553, 205 (1998).

[15] D. F. Page, R. O. Clinton, J. Org. Chem. 27, 218 (1962).